This invention relates to additives for hydraulic cement compositions. More particular, this invention concerns an improvement in additive products for hydraulic cement, especially Portland masonry cement compositions used in mortars, etc., for bonding bricks, blocks, etc.
Portland masonry cements are compositions produced particularly for use by masons in the bonding of bricks, blocks and the like. Such cements are typically mixed prior to use with a fine aggregate, usually sand, and water. It is desirable that the wet mortar have a high degree of "plasticity" for working (e.g. troweling, etc.,) by the mason, as well as other desirable properties such as good "board life", water-repellancy, etc.
Masonry cements are produced by intergrinding Portland cement (containing gypsum for proper setting time regulation), with, generally, from about 35 to 65% (based on the total) of a solid material such as limestone, chalk, talc, pozzolans, clay, gypsum, or combinations of such. Limestone is most often the ingredient interground with the Portland cement because of its good "plasticity"-enhancing properties. Such masonry cements are ground to a greater degree of fineness than most Portland cements intended for use in structural "concretes", which, inter alia, improves "plasticity" of the finished mortar products.
Additive products are sold for mixture with the masonry cement, such additive products being designed to impart certain desirable properties to the masonry cement composition. It is common practice to mix such additive products with the cement during the intergrinding of the cement with the gypsum, limestone, etc.
In U.S. Pat. Nos. 3,865,601 and 3,885,985, additive products of the above type are described. The additives described therein comprise an aqueous oil-in-water emulsion containing water, a water insoluble, water-repelling acid component (e.g. tall oil), an emulsifier (e.g. a salt of such acid), and a setting time-retarding agent (e.g. sucrose). This additive product is ideally dispersible in water (which reduces the risk of it being "overdosed"). The additive preferably contains an air-entraining agent as an additional optional component.
The emulsion additive product described in the aforementioned patents has been successfully utilized in the manufacture of Portland masonry cement compositions in particular by dispersing the additive product in water and adding it to the Portland cement during the grinding thereof. A disadvantage attendant to the shipping and storage of the emulsion additive product is the susceptibility of the product to become destabilized sometimes when exposed to freezing temperatures prior to use. Freezing of the product causes phase separation, resulting, as a practical matter, in the product becoming useless.